Means for testing faulty electric-line insulators and indicating leakage therein



Feb. 17. 1925 7 1,526,770

o. w. BRAIN MEANS FOR TESTING FAULTY ELECTRIC LINE tNSULATORS AND INDICATING LEAKAGE THEREIN FiILed May 22, 1923 Patented Feb. 17, 1925.

UNITED STATES PATENT OFFICE.

ORLANDO WILLIAM BRAIN, OF ASHFIELD, 'NEAR SYDNEY, NEW SOUTH WALES, AUSTRALIA.

MEANS FOR TESTING FAULTY ELECTRIC-LINE INSULATORS AND INDICATING LEAK- AGE THEREIN.

Application filed May 22, 1923. Serial No. 640,671.

To all whom it may concern.-

. Be it known that I, ORLANDO ILLIAM BRAIN, subject of the King of Great Britain and Ireland, residing at 85 Bland Street, Ashfield, near Sydney, New South Vales, Australia, have invented certain new and useful Im )rovements in Means for Testing Faulty Electric-Line Insulators and Indieating Leakage Therein, of which the following is a specification.

The present invention has been devised to offer a practical solution for the problem of ensuring continuity of service in electric lines which are liable to failure consequent on electrical breakdown of insulators. As is known to electrical engineers, no initial electrical test can offer any acceptable assurance on the useful term of life of these insulators. Breakdown in insulating value takes place in many cases sooner or later during service, and no means have been yet proposed for informing the linesmen that an electrical breakdown is threatened or is impending, or that abnormal leakage is taking place at any'insulator. hen failure of an insulator does take place the failure is usually preceded by comparatively heavy leakage'of current through the insulator from the line to the insulator pin. This leakage conducted through the insulator pin to the pole cross arm soon sets up heating, and often the first indication of leakage is displayed by the charring or firing of the cross arm.

It is assumed in practice, and it is prob ably true, that when electrical breakdown of a mechanically sound overhead line insulator takes place it has been preceded for a longer or shorter period by leakage of current from the line to ground through the insulator and pin and cross arm and the pole, and it is'usual to submit line insulators to periodical tests to anticipate insulation failure. For this purpose linesmen' must visit each pole and by means of suitable electrical testing instruments ascertain whether leakage of current is taking place from it. This testing is costly and includes an element of danger, and on the whole is unsatisfactory in the result. On the other handperiodical removal of current from the line to allow of this testing is frequently troublesome and c v ent;

My invention provides an indicator with means for displaying it automatically when abnormal leakage of current occurs; these indicators are observable from ground level so that inspection of the line can be made by a linesman whilst driving or riding. Rapid inspection is thus facilitated, with elimination of danger to the inspectors. The indicator used by me is one which is dependent for its operation on effects produced by leakage current. In practice I use a thermally operated or a thermally released device which is operated or released automatically without opening the line. The local visible indicator is also utilized to complete an electric circuit on a signal line when it is in the displayed position and thereby operate an electric alarm and afford means at a station on the line whereby the place of the failure may be located through appropriate electric measuring instruments. The details of application of the invention most appropriate in particular cases may be left to the judgment of competent electrical engineers.

In applying the invention in the case of pin mounted line insulators supported on pole cross arms, a satisfactory method of carrying out the invention is disclosed in the accompanying sheet of drawings, in whicl1,

Fig. 1 is a sectional elevational view through the release device which is positioned intermediately the insulators on a pole and the indicator on that pole; and

Fig. 2 is a semi-diagrammatic elevational view showing the pole equipment.

The equipment is fitted on every pole on the line. One releaser and indicator may be used for any number of insulators which may be carried on the equipped pole.

10 is the pole, ll wooden cross arms. 12 line insulators of any usual type mounted on metal stud pins which are secured in the cross arms 11. the top of the post or in any other convenient position for supporting an earth line 14. A tap 16 from the line ll is car ried on one or more insulators 15 as may be necessary and is electrically connected to the metal arm 41 which forms the visible indicator. At one end of it this indicator arm 41 is mounted on a pivot insulated from the post 10. The stem pins of the several line insulators on the post are connected to- 13 is an insulator lixed on gether by a wire 17 brought over insulators 18 so that the-leakage fronrallfthe 'lnsul-a tors on-the post is collected.

it on the bottom end of one of the insulator pins ratlt). .forinstance 20:*isa metal: hook" attached to and making good electricalicone ne-ctlon w1th the insulator pm. 21 1s an eye pin in the top of the releaser. This eye pin 1 21 is carried on the hook 20 and suspends the releaserfrom the insulator pin; The release-r comprises a cylindrical metai case-22 closed at the t'o p and open atthe bottom and preferably having its bottom' end '23 belied for the-purpose 0t deflecting rain" drops. 24 is a porcelain'plu'gwhich is in= sertedinto" the larger lower part otthe counterbore'in the case 22" and secured therein bye'mean'sof'cement 275 25 and 2G representing the irregular or roughenedt'aces of the porcelain 24' andof the -metal=- body 22 respectively; a little roughness is desirable in -both t-hese parts to ensure eflective grip forthe' cement fasteningQF. 28 is a washer of thick cloth impregnated with an: insulatingicompound: 29' is a pin- Which passes up through the centreof the porcelain plug 2%, 30 be'ing a collar on this pin which-is contained in sinking in the bot tom end -of the porcelain plug 2 1*, said sinking being filled overwith cement. 32 is an eye formed on the botto-rnendof thepin 29. is a nut on other fastening by which the top endof the pin 29 is secured against the top en-d'ot the porcelain plug 24. I

' 3% *isa varnished paper sleeve inserted in the: upper narrow part of tl1e-co-unte=1-*- bore: :inthe release-r" shell 22;-

is: another varnishedpaper sleeve within. the sleeve 34% 36 is a block of carbon. 37 is a paper cartridgecont aininga charge'of'explosive powder-38u 89 is'a carbon block wh'ieh plugs the open end of the paper cartridge ZST' and makes contact with the explosive powder 38 on its top side; and on its underside makes contact with the t'op' end of theipin 29: 40 is a-hel'i-cal spring abutting:- againstthe top end oftlm'metal shell 22 and bearingdo wn on the top of the carbon block36a 41 is an indicator arm of metalnv-hiclris suspended atits outerend on theieye 32 and at 'it's inner end is supported pivotal-1y: on the post 10 at 42*but is insu'lated'trom the post; 433s a cross arm tocarry the insulator 44-011 which a bare signalwire45 i's strung. When the arm 41 falls to theposition shown in the dotted-line it contacts with the signal lin'e 45,-. connectingtliat line through the earth line: 14 via thetap wire 16. T

A chokeooilet? may; be inserted in the tap wire 16, the function ot-this choke coil being toallow 'flow "of-" leakaig e current, but to pretrentvsurges otcurren-t" passing "through the. line.

The function of the paper sheets 34 and 35 is to insulate the powder charge 38 from the: walls :ofrtheQ lreleaserg 224; The; ftmctaon of'the paper cartridge 37 is to provide a dielectric diaphragm between the powder 38 and: either ot thei carbon contact blocks 36 and 39, the arrangement being such that a leak current from the insulator-0n--:wliiclithe -releasor ishiingcann'ot tind apathbetween the rings 2land'32 'except through the cartridge; When a leaky condition de velops in an insulatorthe releaserterm-inals are under electrical stress, and when-this stress rises above a predeterminedpoint the dielectric37"is pierced and the poWder-38 fired, with the: result-that the porcelain ping 24 is expelled, and'the indicator arm 41 being no longer suspended by it drops by gravity from the normal horizontal position in -which-it isshown-in the full linesi in Fig; Qto the-dotted 1 line-position in that figure: In'the latter position it makescontactwith the signal line 45-, connecting that line: .to earth via the tap wire 16- and theearth line 14 and operating an el'ectric alarmata sta tion; Appropriatetesting instruments con nected onthe signal line'4c5' operate to show at the siguialr station the approximate location of the breakdown; 1 The; powder '38 is a fine grain bla-ck powder which has reason able electrical conductivity A-faul-ty indicator is thus caused by reason of the-leakage through itto produce a report of'iits own1 failure either "solely through the local indicator arm 41 which can be' seen from the-ground, but=also if desired through asignal circuit 45 which is connected when the breakdown occurs and the localisignal is displayed;

The papei sliea-ths: are -preterably var,- nished and the cartridge 37 is made of such material and any'suchthickness tha-ta certain known electricalpotentialdifi'erenceis necessary on the respective sides of it to produce breaking down and puncturingg I Tests made with 1 the apparatu's establish tlie tact -tihat leakcurrents of the order of onemillianrpere -suffice for puncturi-ng the cartridgeandiexplofding the-powder in the rel'easer at any desiredvoltage within-*ordrnary workinga'anges-in a period of leakage ofvery short duration-, that is to"; say one minute or" less The d'ieiectrio value ofthe cartridgemust be selected appropriately to the leakage condition to be indicated-r It is to= be understood that ina'smuclr as the: function of the powder explosion-is to cause expulsion I of the releaser p1ug 24 --so as: thereby to permitthe indicator-armd-l t drop, there maybe substituted -*fer'theexplosive powder any other substance which, responsively to the heating effect of a leak current of known dimensions on it, will operate to break the indicator suspension.

The essence of the invention is the utilization of a leak current through or over a line insulator to open a releaser which is located in proximity to such insulator, and is adapted to cause a visible indicator to be displayed.

Whilst, therefore, the particular construction of releaser which has been illustrated is put forward as an effective device for the carrying out of the invention, it is to be understood that it is not the exclusive means available for that purpose.

If the signal line is fitted with appropriate signalling instruments it would inclicate at a linesmans room or elsewhere required, the fact that a breakdown had occurred by displaying an appropriate signal whenever the signal line 45 is earthed by contact of an indicator arm 41 with it.

When the. device is used under circumstances where the normal leakage current approaches or exceeds one milli-ampere, a high resistance element 48 of suitable form may be connected between thewire 17 connecting the pins of the insulators 12 and the earth wire 16 to prevent operation of the device until a predetermined current of still greater magnitude than the normal leak in service conditions has been reached.

hat I claim as my invention and desire to secure by Letters Patent is 1. An electric line insulator leakage indicator comprising a gravity drop arm, a releaser supporting said arm, a sensitive substance enclosed within said releaser and located in the path of a leak current from an electric line insulator, and means for causing the arm to drop when the sensitive substance is traversed by the leak current.

2. An electric line insulator leakage indicator according to claim 1, in which the releaser is a case sealed with a stopper on which the gravity drop arm is suspended, and contains an explosive substance in a cartridge of dielectric material with contacts at either end of such cartridge one of which contacts is electrically connected to the insulator support and the other to earth.

3. An indicator according to claim 1, comprising a cup like releaser case pendent from and electrically connected with the pin of a line insulator, a plug of electrically insulating material luted into the mouth of said releaser, an earthed gravity drop arm suspended from said plug, and an explosive charge enclosed between contacts at opposite ends of it which contacts are electrically connected to the insulator pin and the drop arm respectively.

4. A device for indicating the insulating efficiency of line insulators in service, comprising a gravity drop earthed indicator which is pivot mounted on a post with its free end suspended by a releaser pendent from the insulator pin, and within the releaser a charge of a substance which when affected by a leak current of predetermined value passing through it from the pin to the indicator expands and breaks the mechanical support which sustains the arm.

In testimony whereof I affix my signature in presence of two witnesses:

ORLANDO WILLIAM BRAIN.

Vitnesses T. K. FLANAGAN, M. R. BENNETT. 

